Surfing the web, I found the following explanations on how to produce the diphthongs [aʊ] and [aɪ]:
"/aʊ/ as in all the words of "How now brown cow!". The starting position is the vowel sound /æ/ as in "at" "bad" or "rat" with tongue front but also low (i.e. mouth open). To make the diphthong the journey for your tongue from front low (mouth very open) to back high (small tight mouth aperture) is a very long excursion. Your jaw will move a lot too."
"/aɪ/ as in sky, buy, cry, tie. The starting position is /æ/, the same sound as in "cat". To make the diphthong you need a big jaw movement, moving the tongue from front open to and front close."
Are these the correct ways to produce these two diphthongs in American English?
The explanation that says that /aʊ/ starts in /æ/ makes sense to me because that's what I hear, but I'm not sure about the second one. I don't think /aɪ/ starts in /æ/.
Could you please tell me in which vowel these two diphthongs start?